Fragment based lead discovery of small molecule inhibitors for the EPHA4 receptor tyrosine kinase

The in silica identification, optimization and crystallographic characterization of a 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine scaffold as an inhibitor for the EPHA4 receptor tyrosine kinase is described. A database containing commercially available compounds was subjected to an in silica screening procedure which was focused on finding novel, EPHA4 hinge binding fragments. This resulted in the identification of 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine derivatives as EPHA4 inhibitors. Hit exploration yielded a compound with 2 mu M (IC50) affinity for the EPHA4 receptor tyrosine kinase domain. Soaking experiments into a crystal of the EPHA4 kinase domain gave a 2.11 angstrom X-ray structure of the EPHA4 - inhibitor complex, which confirmed the binding mode of the scaffold as proposed by the initial in silica work. The results underscore the strength of fragment based in silica screening as a tool for the discovery of novel lead compounds as small molecule kinase inhibitors. (C) 2011 Elsevier Masson SAS. All rights reserved.